Planetary reducer and wheel bearing unit

ABSTRACT

A motor vehicle integral speed reduction and wheel mounting unit having a driven rotatable axle pivot member with axially spaced annular bearings mounted on the outer surface. An annular fixed axle housing has an inner surface mounted on the bearings. A ring gear is formed on the axial portion of the inner surface of the axle housing located between the bearings. Intermediate shafts are rotatably mounted in the axle pivot member and a gear is fixed on each intermediate shaft. Each gear is located partially within a radial recess formed in the axle pivot member. One end of each intermediate shaft extends out of the axle pivot member and is connected to a drive shaft by a planet gear fixed on the end of the intermediate shaft.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to an integral speed reduction and wheelmounting unit for a motor vehicle and, more particularly, to an integralspeed reduction and wheel mounting unit including an axle pivot member,spaced annular bearings located on the axle pivot member and an axlehousing mounted on the annular bearings so that either the axle pivotmember or the axle housing can function as a driven hub.

2. Description of Related Prior Art

The prior art discloses many different arrangements of such units. Forexample, German Patent No. DE-OS 28 43 597 discloses a wheel bearingunit designed as a two-row annular bearing wherein the external bearingsurfaces of the two rows of bearings are cast on the inside of the axlehousing which is a stationary hub bracket and, therefore, also has afastening flange cast thereon. This design provides a system having arelatively small number of component parts. However, the disadvantage ofa wheel bearing unit according to this prior art design is that thetorque amplification between the drive engine of the vehicle and thedriven vehicle wheels takes place upstream of the wheel bearing unit anda separate transmission is required which significantly increases theamount of space required and the weight of the vehicle. Additionally, awheel bearing unit according to this prior art design requirescost-intensive fabrication and installation operations. Moreover, thedesign requires the transmittal of large torques to the wheel by atransmission having complex and expensive shafts with universal joints.

U.S. Pat. No. 4,275,616 entitled "Hydraulic Wheel Drive" discloses agear train inside a wheel drive on a machine tool. The design iscompletely different from the wheel bearing units of the prior art whichare used in the mass production of motor vehicles. The axle housing isdesigned as a hub and is rotationally mounted on the axle pivot memberwhich serves as the hub bracket. The end surface of the axle pivotmember adjacent to the wheel is the stationary plate of a planetary geartrain. The planetary gear train is an axial extension of the hub bracketwhich makes the arrangement quite long which requires a significantamount of space. Moreover, if the motor vehicle is equipped with dualtires a severe load is placed on the roller bearings since the lever armon which the wheel forces are exerted is very long.

U.S. Pat. No. 4,896,740 entitled "Wheel Bearing Support" discloses awheel head for the live front axle of a farm tractor in which the axlehousing is rotationally mounted on a stationary axle pivot member. Theinside of the rotating axle housing provides a ring gear of a step-downtransmission between spaced roller bearings. The ring gear and thus theaxle housing or hub are connected by an eccentrically located driveshaft and by two intermediate wheels mounted on the stationary axlepivot member or hub bracket. This design also occupies a great deal ofspace and, additionally, is restricted to use in a system in which theaxle pivot member is stationary and the axle housing rotates.

SUMMARY OF THE INVENTION

The object of the invention is to provide an integral speed reductionand wheel mounting unit of the type described above, which is combinedwith a gear train in a compact and economical manner.

This object of the invention can be achieved by locating a ring gear onthe inside of the axle housing between two spaced bearings and by havingthe ring gear engage at least one gear which is partly located in aradial recess formed in the axle pivot member and is non-rotationallyconnected to an intermediate shaft having both of its ends extendinginto the axle pivot member. At least one end of the intermediate shaftextends out of the axle pivot member and is operatively connected to adrive shaft which is coaxial with the axis of rotation of the integralspeed reduction and wheel mounting unit. Accordingly, an essentialaspect of the invention is to integrate torque amplification into thecenter of an integral speed reduction and wheel mounting unit. For thispurpose, the advantages of an integral speed reduction and wheelmounting unit, such as small size, low weight and low cost, are retainedwhile significant savings in size, weight and cost are achieved comparedwith prior art transmission and wheel bearing unit arrangements.

In the integral speed reduction and wheel mounting unit according to theinvention, the axle housing can be a rotating hub, in which case theaxle pivot member is the stationary hub bracket. However, the axle pivotmember can be a rotating hub, in which case the axle housing is thestationary hub bracket. In one preferred embodiment of the invention,the axle pivot member is a rotating hub and the axle housing is astationary hub bracket connected to the vehicle. This arrangement iscompatible with conventional commercially available wheel bearing units.

The connection between the drive shaft and the intermediate shaft can bedesigned, for example, as a transmission. However, it is preferred thatthe drive shaft is a sun gear of a planetary gear train and engages withat least one planet gear which is fixed on the end of an intermediateshaft which extends out of the axle pivot member and forms a part of theplanetary gear train. In this embodiment of the invention, there are twoplanet gears in the planetary gear train. One planet gear is engagedwith the sun gear and the other planet gear is located partially withina recess formed in the axle pivot member and is engaged with a ringgear. The sun gear and the first planet gear form an adapter/convertergear train, which is upstream of the final gear train located betweenspaced annular bearings of the integral speed reduction and wheelmounting unit. This design has the advantage that the step-down in thefinal gear train can always be the same for various applications,because the total step-down can be changed by changing the step-down inthe adapter/converter gear train. The sun wheel can be fixed on thedrive shaft or it can be cast directly on the drive shaft. For ease offabrication and installation, it is favorable if the annular ring gearis cast on the inner surface of the axle housing.

If the planetary gear train is designed as a train of toothed gears andthe number of teeth of the two planet gears located in a common planeare different, the result is a one-and-one-half-stage planetary geartrain.

In theory, the intermediate shaft can extend out of either axial ends ofthe axle pivot member with regard to the shortest possible mosttorsion-proof drive shaft. However, in the most favorable arrangement,the intermediate shaft only extends out of the end of the axle pivotmember opposite the end adjacent the wheel. In this arrangement, theaxle pivot member has high bending strength and torsional strength inthe vicinity of the internal planet gears.

In another embodiment of the invention, a clutch mechanism is mounted onone end of the drive shaft. Depending upon the end of the axle pivotmember from which the intermediate shaft extends, the clutch mechanismcan be located internally or externally. In a particularly favorablearrangement, the intermediate shaft extends out of the end of the axlepivot member adjacent to the wheel and the drive shaft passes axiallythrough the center of the axle pivot member. The intermediate shaft andthe drive shaft are operatively connected on the end of the axle pivotmember adjacent to the wheel and the clutch mechanism is located betweenthe drive shaft and the axle pivot member. The clutch mechanism and theadapter/converter gear train are easily accessible for service andmaintenance.

The clutch mechanism is a hydraulically-operated, multiple-toroid,spring-brake system located in a bracket which can be bolted, along witha wheel rim, to the axle pivot member. The clutch mechanism is easilyaccessible after the removal of the wheel rim. The clutch mechanismrequires no projecting fluid lines or actuating cables which avoidsexposure to potential damage and corrosive influences. The drive shaftis formed with a longitudinal axial passage for supplying a pressuremedium to the multi-toroid brake mechanism.

In one aspect of the invention, the bearings are annular ball bearingswith the same nominal diameter in order to achieve the widest possiblebearing base.

In order to reduce the number of components to be assembled, the outerrace of each bearing is cast integrally on the inner surface of the axlehousing. For this purpose, when the axle housing functions as the hubbracket, a radially extending annular mounting flange is cast on theouter surface.

An extremely compact design, in which the integral speed reduction andwheel mounting unit has only a few components, is achieved if the outerraces of the bearings; the ring gear of the planetary gear train; andthe mounting flange are all cast on appropriate surfaces of the axlehousing.

A complete understanding of the invention will be obtained from thefollowing description when taken in connection with the accompanyingdrawing figures wherein like reference characters identify like partsthroughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal section through an integral speed reduction andwheel mounting unit according to the invention;

FIG. 2 is a longitudinal section through a unit according to the priorart;

FIG. 3 is the integral speed reduction and wheel mounting unit shown inFIG. 1 and a longitudinal section through an electrically driven liveaxle;

FIG. 4 is a longitudinal section of a second embodiment of an integralspeed reduction and wheel mounting unit according to the invention; and

FIG. 5 is a longitudinal section of a third embodiment of a unitaccording to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1 of the drawings, the integral speed reductionand wheel mounting unit according to the invention has an axle housing 1which functions as rotatable hub or a stationary hub bracket and isprovided on its outer surface with an annular mounting flange 2 havingspaced bolt holes formed therein. An axle pivot member 3 is rotationallymounted within axle housing 1 by two axially spaced annular rollerbearings 4 and 5. The outer annular races of bearings 4 and 5 are caston axle housing 1, and the inner races of bearings 4 and 5 are formed byannular rings mounted on the exterior surface of axle pivot member 3.The annular roller bearings can be axially adjusted in relation to oneanother on the axle bearing member by a bearing nut 6 which is threadedon the exterior surface of one end of the axle pivot member.

A ring gear 7 is located between bearings 4 and 5 and is preferably castintegrally on the inner surface of axle housing 1. Ring gear 7 engageswith planet gears 8 which are partially located in pocket-shaped radialrecesses 9 formed in axle pivot member 3. Each planet gear 8 is fixed onan intermediate shaft 10 which is rotatably mounted in axle pivot member3. One end of each intermediate shaft extends out of axle pivot member 3on the end of the axle pivot member opposite wheel rim 13. The outer endof each intermediate shaft 10 is operatively connected to a drive shaft11 by a planet gear 12 which is fixed to the shaft. Drive shaft 11functions as a sun gear in a one-and-one-half stage planetary gear trainwhich drives planet gears 12 which are fixed on intermediate shafts 10.Gears 8 located in recesses 9 form second planet gears, which areconnected to the same shafts as planet gears 12. The sun gear and planetgears 12 form an adapter/converter gear train, while gears 8 whichrotate in synchronization with planet gears 12 and ring gear 7 form afinal gear train. This gear train combination is called aone-and-one-half-stage planetary gear train. The planetary gear trainpreferably includes three planet gears 12 and three planet gears 8.

The integral speed reduction and wheel mounting unit according to theinvention operates according to the following. Drive shaft or sun gear11 drives planet gears 12 and thus intermediate shafts 10. Gears 8 arefixed on intermediate shafts 10 and engage ring gear 7 so that as axlepivot member or hub 3 in which intermediate shafts 10 are mounted isrotated, the wheel which is bolted to the axle pivot member alsorotates. FIG. 1 shows only the rim 13 of the wheel.

The integral speed reduction and wheel mounting unit according to theinvention results in both a reduction of the speed and an amplificationof the torque transmitted by drive shaft 11. The arrangement illustratedin FIG. 1 is suitable for a reduction ratio between the rotary speed ofdrive shaft 11 and the rotary speed of the wheel of approximately 16:1.

FIG. 2 of the drawings shows a prior art driven unit without torqueamplification which is designed for the same rim diameter as theintegral speed reduction and wheel mounting unit of the inventionillustrated in FIG. 1 of the drawings. The dimensions of the integralspeed reduction and wheel mounting unit according to the invention areessentially the same as the dimensions of a unit of the prior artwithout torque amplification, particularly in the radial direction. Theload-bearing capacity is thereby equivalent, because the annularbearings in the integral speed reduction and wheel mounting unitaccording to the invention, although they have smaller dimensions, arelocated on a bearing race which has a larger diameter. A comparison ofFIG. 1 with FIG. 2 also shows that when an equal torque is delivered tothe wheel, a significantly smaller diameter drive shaft is necessary inthe wheel bearing unit according to the invention, which is both compactand lightweight.

FIG. 3 of the drawings shows an integral speed reduction and wheelmounting unit according to the invention connected as the final powertake-off of an electrically-driven live axle 14. As a result of theextremely compact design of the wheel bearing unit, it is possible touse large electric motors in a relatively small space which provides anelectrically-driven live axle with a higher power density. An integralspeed reduction and wheel mounting unit according to the invention canalso be connected to other drive systems.

FIG. 4 of the drawings shows a second embodiment of an integral speedreduction and wheel mounting unit according to the invention wherein aclutch mechanism is located between drive shaft 11 and axle pivot memberor hub 3. Intermediate shafts 10 are located on the end of the axlepivot member adjacent to the wheel, i.e., the outer end, and they extendout of the axle pivot member to mount planet gears 12. A bracket 15 isbolted onto axle pivot member 3 along with wheel rim 13. Of course, itis also possible to connect bracket 15 to axle pivot member 3 by its ownindependent fastening means. Multiple annular members 16 are fastened inbracket 15 in a non-rotating fashion so that they can movelongitudinally axially in relation to the brake bracket and to a discbracket 17 non-rotationally fastened to drive shaft 11. The multipleannular members 16 are pressurized against the force of a coil spring 18by a hydraulic piston 19. A pressure chamber 20 is provided forpressurized fluid supplied through a longitudinal control passage 21 indrive shaft 11 to actuate piston 19. The multiple annular members andthe adapter/converter gear train formed by the sun gear and planet gears12 operate in an oil bath.

FIG. 5 of the drawings shows a third embodiment of a unit according tothe invention wherein the member 3' functions as a stationary hubbracket and the wheel rim 13' is bolted to the outer annular memberwhich functions as a rotating hub. Bearings 4' and 5' which are axiallyspaced along the member 3' mount the rotary hub on the stationary hubbracket 3'. A bearing nut 6' is threaded onto the free end of thestationary hub bracket 3' to hold the rotating hub in place against thebearings 4' and 5'. A ring gear is located on the rotating hub betweenbearings 4' and 5' and is preferably cast on the inner surface of therotating hub. The ring gear engages planet gears 8' which are partiallylocated in pocket-shaped radial recesses 9' formed in the stationary hubbracket 3'. Each planet gear 8' is fixed on an intermediate shaft 10'and a planet gear 12' is fixed on the outer end of each intermediateshaft 10'. The planet gears 12' are driven by drive shaft 11 whichfunctions as a sun gear.

While embodiments of the invention have been described in detail herein,it will be appreciated by those skilled in the art that variousmodifications and alternatives to the embodiments could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements are illustrative only and is not limiting as tothe scope of the invention which is to be given the full breadth of theappended claims and any and all equivalents thereof.

I claim:
 1. An integral speed reduction and wheel mounting unit adaptedto support a wheel on a motor vehicle, said unit comprising an axlepivot member having an outer surface, axially spaced annular bearingsmounted on said outer surface of said axle pivot member, an annular axlehousing having an inner surface mounted on said axially spaced bearings,whereby said axle pivot member is a driven member, a ring gear formed onsaid inner surface of said axle housing located between said axiallyspaced bearings, at least one intermediate shaft rotatably mounted insaid axle pivot member, at least one radial recess formed in said axlepivot member and a planet gear fixed on said at least one intermediateshaft located partially within said radial recess and meshing with saidring gear, one end of said at least one intermediate shaft extending outof said axle pivot member and means for operatively connecting said oneend of said at least one intermediate shaft to a drive shaft coaxialwith the axis of rotation of said axle pivot member, whereby rotation ofsaid at least one intermediate shaft rotates said axle pivot memberrelative to said annular axle housing.
 2. An integral speed reductionand wheel mounting unit as set forth in claim 1 wherein said axlehousing includes a radially extending annular external mounting ringadapted to be fastened to a vehicle, and wherein said axle pivot memberis a rotating hub.
 3. An integral speed reduction and wheel mountingunit as set forth in claim 1 wherein said means for operativelyconnecting said one end of said at least one intermediate shaft to adrive shaft is a planet gear fixed on said at least one end of saidintermediate shaft extending out of said axle pivot member for operativeconnection with a drive shaft, whereby the drive shaft functions as thesun gear of a planetary gear train.
 4. An integral speed reduction andwheel mounting unit as set forth in claim 2 wherein said means foroperatively connecting said one end of said at least one intermediateshaft to a drive shaft is a planet gear fixed on said one end of saidintermediate shaft extending out of said axle pivot member for operativeconnection with a drive shaft, whereby the drive shaft functions as thesun gear of a planetary gear train.
 5. An integral speed reduction andwheel mounting unit as set forth in claim 1 wherein said ring gear isformed on said inner surface of said axle housing.
 6. An integral speedreduction and wheel mounting unit as set forth in claim 2 wherein saidring gear is formed on said inner surface of said axle housing.
 7. Anintegral speed reduction and wheel mounting unit as set forth in claim 3wherein said ring gear is formed on said inner surface of said axlehousing.
 8. An integral speed reduction and wheel mounting unit as setforth in claim 1 wherein said one end of said at least one intermediateshaft extends out of the end of said axle pivot member spaced from awheel.
 9. An integral speed reduction and wheel mounting unit as setforth in claim 2 wherein said one end of said at least one intermediateshaft extends out of the end of said axle pivot member spaced from awheel.
 10. An integral speed reduction and wheel mounting unit as setforth in claim 3 wherein said one end of said at least one intermediateshaft extends out of the end of said axle pivot member spaced from awheel.
 11. An integral speed reduction and wheel mounting unit as setforth in claim 4 wherein said one end of said at least one intermediateshaft extends out of the end of said axle pivot member spaced from awheel.
 12. An integral speed reduction and wheel mounting unit as setforth in claim 1 including adjustable coupling means extending between adrive shaft and said axle pivot member for varying the rotational speedof said axle pivot member.
 13. An integral speed reduction and wheelmounting unit as set forth in claim 2 including adjustable couplingmeans extending between a drive shaft and said axle pivot member forvarying the rotational speed of said axle pivot member.
 14. An integralspeed reduction and wheel mounting unit as set forth in claim 3including adjustable coupling means extending between a drive shaft andsaid axle pivot member for varying the rotational speed of said axlepivot member.
 15. An integral speed reduction and wheel mounting unit asset forth in claim 4 including adjustable coupling means extendingbetween a drive shaft and said axle pivot member for varying therotational speed of said axle pivot member.
 16. An integral speedreduction and wheel mounting unit as set forth in claim 5 includingadjustable coupling means extending between a drive shaft and said axlepivot member for varying the rotational speed of said axle pivot member.17. An integral speed reduction and wheel mounting unit as set forth inclaim 1 wherein said one end of said at least one intermediate shaftextends out of the end of said axle pivot member close to a wheel andincluding a drive shaft extending through the center of said axle pivotmember, and means for operatively connecting said intermediate shaft andsaid drive shaft on the end of said axle pivot member close to a wheel,and further including adjustable coupling means mounted on said driveshaft between said drive shaft and said axle pivot member forcontrolling the speed of rotation of said axle pivot member.
 18. Anintegral speed reduction and wheel mounting unit as set forth in claim 2wherein said one end of said at least one intermediate shaft extends outof the end of said axle pivot member close to a wheel and including adrive shaft extending through the center of said axle pivot member, andmeans for operatively connecting said intermediate shaft and said driveshaft on the end of said axle pivot member close to a wheel, and furtherincluding adjustable coupling means mounted on said drive shaft betweensaid drive shaft and said axle pivot member for controlling the speed ofrotation of said axle pivot member.
 19. An integral speed reduction andwheel mounting unit as set forth in claim 3 wherein said one end of saidat least one intermediate shaft extends out of the end of said axlepivot member close to a wheel and including a drive shaft extendingthrough the center of said axle pivot member, and means for operativelyconnecting said intermediate shaft and said drive shaft on the end ofsaid axle pivot member close to a wheel, and further includingadjustable coupling means mounted on said drive shaft between said driveshaft and said axle pivot member for controlling the speed of rotationof said axle pivot member.
 20. An integral speed reduction and wheelmounting unit as set forth in claim 4 wherein said one end of said atleast one intermediate shaft extends out of the end of said axle pivotmember close to a wheel and including a drive shaft extending throughthe center of said axle pivot member, and means for operativelyconnecting said intermediate shaft and said drive shaft on the end ofsaid axle pivot member close to a wheel, and further includingadjustable coupling means mounted on said drive shaft between said driveshaft and said axle pivot member for controlling the speed of rotationof said axle pivot member.
 21. An integral speed reduction and wheelmounting unit as set forth in claim 17 wherein said adjustable couplingmeans includes a plurality of axially shiftable annular members andhydraulically-actuated, spring-loaded means for axially shifting saidannular members, a brake bracket, and means for attaching said brakebracket to said axle pivot member.
 22. An integral speed reduction andwheel mounting unit as set forth in claim 21 wherein said drive shafthas a longitudinal axial passage formed therein for supplying a pressuremedium to said hydraulically-actuated, spring-loaded means to counteractthe force of said spring-loaded means.
 23. An integral speed reductionand wheel mounting unit as set forth in claim 21 wherein each of saidannular bearings includes a plurality of ball bearings havingsubstantially the same diameter.
 24. An integral speed reduction andwheel mounting unit as set forth in claim 1 wherein the outer race ofeach of said annular bearings is formed on the inner surface of saidaxle housing.
 25. An integral speed reduction and wheel mounting unitadapted to support a wheel on a motor vehicle, said unit comprising anaxle pivot member having an outer surface, axially spaced annularbearings mounted on said outer surface of said axle pivot member, anannular axle housing having an inner surface mounted on said axiallyspaced bearings, whereby said annular axle housing is a driven member, aring gear formed on said inner surface of said annular axle housinglocated between said axially spaced bearings, at least one intermediateshaft rotatably mounted in said axle pivot member, at least one radialrecess formed in said axle pivot member and a planet gear fixed on saidat least one intermediate shaft located partially within said radialrecess and meshing with said ring gear, one end of said at least oneintermediate shaft extending out of said axle pivot member and means foroperatively connecting said one end of said at least one intermediateshaft to a drive shaft coaxial with the axis of rotation of said annularaxle housing, whereby rotation of said at least one intermediate shaftrotates said annular axle housing relative to said axle pivot member.